Embodiments of the present application generally relate to fault detection. More particularly, but not exclusively, embodiments of the present application relate to fault detection and the activation of protection devices in electric power systems.
Intelligent Electronic Devices (IEDs) are microprocessor-based devices used by the electric power industry to control power system switching devices, such as, for example, circuit breakers and reclosers, among other devices. With the standardization by the International Electrotechnical Commission (IEC) of the IEC 61850 process bus, many modern IEDs support voltage and current inputs in a digital format, as Sampled Value (SV) streams transmitted as Ethernet packets on the process bus. In implementations according to the IEC 61850-9-2 specifications, a merging unit (MU) is the device that samples the analog measurements, such as, for example, voltages and currents, of the primary high voltage power circuit, encodes the measurement values into Ethernet packets, and injects them onto the process bus. The IED can receive these SV packets from the process bus, and process and use the SV as inputs to its various fault detection and protection functions.
Primary functions of at least certain IEDs can be to detect the occurrence of a fault on the primary circuit and to issue a trip command to activate a switching device that can disconnect the faulty or shorted parts of the circuit. During such processes, the analog inputs to the MUs and the associated digitized SV packets can be critical to the proper operation decision(s) of the IEDs. Moreover, proper operation of IEDs can be based, at least part, on the accuracy, as well as the authenticity, of the information contained in the SV packets.
Additionally, traditionally, most fault detection algorithms in modern IEDs rely on monitoring of fundamental sinusoidal voltage and current, also referred to as phasors, quantities for fault detection. Thus, at least certain information relating to fast electromagnetic transients that propagate over a primary circuit in response to a fault or short circuit are usually suppressed by digital or analog filters prior to an evaluation of the measurements for fault detection. As a result, traditional fault detection and protection systems often simply ignore fault transients.
Further, compared to at least earlier protection systems that relied on hardwired analog inputs, digitized SV streams and Ethernet technology can have certain susceptibility to cyber-attacks, including, for example, illicit attacks that can be directed to at least the digitized sample value data. For example, in at least certain systems, once gaining access to the process bus and/or to a merging unit, an attacker can modify the SV packets received by the corresponding IED, and thus can manipulate the protection system, which can potentially cause relatively serious consequences to the associated power grid. For example, a false trip on normally healthy circuits could cause the system to weaken in such a way that might lead to localized or regional grid collapse. Accordingly, techniques and devices are needed for securing the IED system against cyber-attacks on sampled value data used for fault detection.